[mlir][Transforms] GreedyPatternRewriteDriver: Add flag to control constant CSE'ing

By default, the greedy pattern rewrite driver CSE's constant ops. If an op is CSE'd with an op in a parent region, the op is effectively "hoisted". Over the last years, users have described situations where this is not desirable/necessary. This commit adds a new flag to `GreedyRewriteConfig` that controls CSE'ing of constants. For testing purposes, it is also exposed as a canonicalizer pass flag.